It looks like movement (primarily vertical) during the exposure. I understand you think the tripod was steady, but I think the parallel doubled mountain range and background seems to indicate that during the exposure the camera moved.

EDIT: Given the updated question and example, since right now this is the upvoted, wanted to clarify since it appears to have a specific cause not just vibration.

It appears the VC is not maintaining control during the entire exposure. My GUESS is that it's timing out in some fashion and re-centering; it might also be defective. Lens based optical vibration reduction works by shifting one or more lens elements to track (or more precisely track opposite) of vibration. The effect means the field of view is shifted during exposure, ideally to keep it in one place. It is possible that it is timing out, and re-centering back to some neutral position. It is possible it is defective and "flops" in some fashion after a given time. Testing a different VC lens might tell you if this is a "feature". All that said, most vendors recommend vibration control be turned off when locked down on a tripod; a few lenses may have a "tripod mode". If it is working at more typical stabilization shutter speeds (say 1/30th), it is likely not worth pursuing.

An interesting way to tell how image stabilization interacts with long exposure is to get a dark night and lock down on a tripod and shoot a bright star for a long exposure (adjust ISO as needed to get a dark sky and thin line). Ideally you get a perfectly straight line. Rotate the camera 90 degrees and shoot again; still should be a straight line. Both regular vibration (e.g. wind) and any optical stabilization impacts can be seen in that, effectively graphed over time, and the 90 degree flip will tell you if the stabilization is different in different orientations (note some lenses have a "mode" for active or normal or similar that can affect this also). This will let you see, for example, if it times out at 10 seconds or something consistent, with a sudden movement (my guess), or if it is just jittery. Reading the manual (lens or camera) to see if there's any comment on timeout may help also.